DOS 2.10 doesn't have enough stack space so swap in our own before dispatching commands

Author: FozzTexx

fujicom/fujicom.c

@@ -20,7 +20,7 @@
 #define TIMEOUT_SLOW	15 * 1000
 #define MAX_RETRIES	5
 #ifndef SERIAL_BPS
-#define SERIAL_BPS      9600
+#define SERIAL_BPS      115200
 #endif /* SERIAL_BPS */
 
 PORT fn_port;

sys/dispatch.c

@@ -8,6 +8,15 @@
 
 #undef DEBUG
 
+#define STACK_SWAP
+#ifdef STACK_SWAP
+#define STACK_SIZE 1024
+char our_stack[STACK_SIZE];     /* our internal stack */
+uint16_t dos_ss;                    /* DOS's saved SS at entry */
+uint16_t dos_sp;                    /* DOS's saved SP at entry */
+uint16_t our_ss, our_sp;
+#endif /* STACK_SWAP */
+
 #define disable() _asm { cli }
 #define enable() _asm { sti }
 
@@ -56,23 +65,55 @@ void far Interrupt(void)
 {
   push_regs();
 
+#ifdef STACK_SWAP
+  // Save ss:sp and switch to our internal stack.
+
+  our_sp = (FP_OFF(our_stack) + 15) >> 4;
+  our_ss = FP_SEG(our_stack) + our_sp;
+  our_sp = STACK_SIZE - 2 - (((our_sp - (FP_OFF(our_stack) >> 4)) << 4)
+                             - (FP_OFF(our_stack) & 0xf));
+
+  _asm {
+    mov dos_ss, ss;
+    mov dos_sp, sp;
+
+    mov ax, our_ss;
+    mov cx, our_sp;
+
+    // activate new stack
+    //cli;
+    mov ss, ax;
+    mov sp, cx;
+    //sti;
+  }
+#endif /* STACK_SWAP */
+
   if (fpRequest->command > MAXCOMMAND
       || !(currentFunction = dispatchTable[fpRequest->command])) {
-    fpRequest->status = DONE_BIT | ERROR_BIT | UNKNOWN_CMD;
+    fpRequest->status = ERROR_BIT | UNKNOWN_CMD;
   }
   else {
 #ifdef DEBUG
-    printDTerm("Command 0x$");
-    printHex(fpRequest->command, 2, '0');
+    consolef("Command 0x%02x", fpRequest->command);
 #endif
     fpRequest->status = currentFunction(fpRequest);
 #ifdef DEBUG
-    printDTerm(" result: 0x$");
-    printHex(fpRequest->status, 4, '0');
-    printDTerm("\r\n$");
+    consolef(" result: 0x%04x\n", fpRequest->status);
 #endif
   }
 
+  fpRequest->status |= DONE_BIT;
+
+#ifdef STACK_SWAP
+  // Switch the stack back
+  _asm {
+    //cli;
+    mov ss, dos_ss;
+    mov sp, dos_sp;
+    //sti;
+  }
+#endif /* STACK_SWAP */
+
   pop_regs();
   return;
 }

sys/init.c

@@ -93,7 +93,7 @@ uint16_t Init_cmd(SYSREQ far *req)
 
     req->init.num_units = FN_MAX_DEV;
 
-    for (idx = 0; idx < FN_MAX_DEV; idx++) {
+    for (idx = 0; idx < req->init.num_units; idx++) {
       /* 5.25" 360k BPB */
       fn_bpb_table[idx].bps = 512;
       fn_bpb_table[idx].spau = 2;
@@ -160,7 +160,7 @@ uint8_t get_set_time(uint8_t set_flag)
 
     intdos(&regs, &regs);
 
-    consolef("MS-DOS Time now set from FujiNet\n$");
+    consolef("MS-DOS Time now set from FujiNet\n");
   }
 
   return 0;